Long March 3B/E launching APStar-9

Tianhui 4 | Long March 2D

Lift Off Time
December 29, 2021 – 11:13 UTC | 19:13 BJT
Mission Name
Tianhui 4, the first Tianhui 4 Earth observation satellite
Launch Provider
(What rocket company launched it?)
China Great Wall Industry Corporation (CGWIC)
(Who paid for this?)
Chinese Ministry of Defense
Long March 2D
Launch Location
Site 9401 (SLS-2), Jiuquan Satellite Launch Center, China
Payload mass
Unknown, up to 1,300 kg (2,900 lb) to Sun-synchronous orbit
Where did the satellite go?
~500 km Sun-synchronous orbit
Did they attempt to recover the first stage?
No, the boosters of the rocket are not recoverable
Where did the first stage land?
It crashed back over land in North-West China
Did they attempt to recover the fairings?
No, the fairings are not recoverable
Were the fairings new?
This will be the:
– 57th flight of a Long March 2D
– 54th Chinese launch of 2021
– 142nd orbital launch attempt of 2021
Where to watch
No replay is available

How Did It Go?

The China Great Wall Industry Corporation successfully launched the Tianhui 04 satellite atop a Long March 2D. It is an Earth observation satellite deployed into a 490 km by 505 km Sun-synchronous orbit.

Tianhui Satellites

The Tianhui (or “sky drawing”) constellation of satellites are Earth observation satellites built by Dong Feng Hong and operated by the People’s Liberation Army, which is a part of the Chinese Ministry of Defense. The Tianhui 4 satellite will monitor the ground in both the visible and infrared spectrum using two cameras. With these cameras, the satellite has a resolution of under five meters and a field of view of roughly 25°. The satellite will also survey human activities.

Due to the nature of the payload, very little is known about the actual satellite. However, it is known that the satellite is equipped with two solar arrays and the two aforementioned cameras.

The Tianhui 4 mission is a follow up to the Tianhui-1 missions, which launched as recently as July of 2021.

What Is The Long March 2D?

The Long March 2D (also known as the Chang Zheng 2D, CZ-2D and LM-2D), is a two-stage rocket, predominantly used for launching satellites to low-Earth orbit (LEO) and Sun-synchronous-orbit (SSO). The Long March 2D is a two-stage version of the Long March 4, and is the smallest of all the active Long March rocket series.

The rocket’s maiden flight was on August 9, 1992, and it has since had a near perfect launch history, with the only incident being a partial failure on December 28, 2016.

Long March 2D
The Long March 2D (Credit: Xinhua)

First Stage

The first stage is 27.91 m in length, and uses four YF-21C engines. YF-21C is the name given to the engine when it is part of a module comprised of four YF-20C engines. The engines burn dinitrogen tetroxide (N2O4) and unsymmetrical dimethylhydrazine (UDMH) in a gas generator cycle. Each engine produces 731 kN of thrust at sea level, with a specific impulse (ISP) of 259 seconds. In vacuum this is 816 kN of thrust with an ISP of 289 seconds.

Second Stage

The second stage is 10.9 m in length, and uses one YF-24C engine, which similarly to the first stage engines, burns dinitrogen tetroxide (N2O4) and unsymmetrical dimethylhydrazine (UDMH) in a gas generator cycle. The name YF-24C means it is part of a module comprising a YF-22 engine and a YF-23 vernier.

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